The purpose of slots in wide copper metal structures is to release thermal stress and reduce dishing effects during copper chemical mechanical polishing (CMP).
U.S. Pat. No. 6,251,786 B1 to Zhou et al. describes a dual damascene process with reduced dishing.
U.S. Pat. No. 6,358,831 B1 to Liu et al. describes a bonding pad process that reduces dishing.
U.S. Pat. No. 6,258,711 B1 to Laursen describes a metal planarization process.
U.S. Pat. No. 6,294,471 B1 to Tseng describes a chemical mechanical process (CMP) for a conductive structure.